What's the difference between a spouse and an espoused partner?

This was likely just an inadvertent error by an editor. The link provided no longer shows (espoused 2009; separated 2012) but dated 2009 - 2012 as of April 27, 2019.

Determining the start of a common law marriage varies significantly by jurisdiction. But it is something that often occurs retrospectively after a specified period of cohabitation, and the period required may be shorter in some places if there is a child.

So an unmarried domestic partner may become an espoused partner after a few years. While for legal reasons the marriage may be held to have commenced when they moved in together, it is not accurate at that point to say they married on the date they moved in. So it would be awkward, if not inaccurate, to use the listing form of married 2009, divorced 2012 for a cohabitation during this period that eventually met the relevant jurisdiction's criteria for common law marriage.